As part of the "NIH/DC Initiative to Reduce Infant Mortality" a program of research aimed at increasing the proportion of infants and children in the District of Columbia who are age-appropriately immunized has been developed. This program of research includes both epidemiologic and intervention (efficacy) studies. The first year (phase I) includes needs assessment and feasibility studies in addition to a prospective cohort study examining determinants of immunization status at 2-3 month of age. The findings from this phase will be used in the planning and execution of a larger cohort study as well as an intervention study in phase II. Investigators include epidemiologists, behavioral scientists, health care providers and administrators. The program of research was developed with input from the variety of perspectives represented by the investigators and the proposed studies have the potential to benefit from a unique blend of epidemiology, behavioral science, and public health and health care practice. It is our intent to develop interventions and identify determinants that are relevant to public health practice in inner cities across the US. This report focuses on the phase I epidemiologic studies.